Refrigerant flow control



Nov. 15, 1966 H. G. VANDERLEE REFRIGERANT FLOW CONTROL Filed m. 14, 1964 FIG.

INVENTOR HAROLD C. VANDERLEE BY W H \5 ATTORUEY United States Patent 3,285,032 REFRIGERANT FLOW CONTROL Harold G. Vanderlee, Tyler, Tex., assignor to General Electric Company, a corporation of New York Filed Dec. 14, 1964, Ser. No. 418,152 3 Claims. (Cl. 62-225) The present invention relates to refrigeration systems and is more particularly concerned with improved flow control means for regulating the flow of refrigerant to the evaporator component.

Refrigeration systems currently marketed generally control the flow of refrigerant from the condenser to to the evaporator by means of an expansion valve or by means of a fixed flow restrictor such as a capillary tube. Expansion valves, particularly the'thermostatic types of expansion valves, usually regulate well but are expensive. For this reason fixed restrictors have been extensively used even though they tend to overfeed or flood the evaporator at high condenser pressure and low evaporator pressure and to underfeed or starve the evaporator at below normal condenser pressure and above normal evaporator pressure. This tendency to either flood or starve the evaporator is exaggerated when the system charge varies from the optimum charge and is also exaggerated by variations in the distance, particularly the vertical distance, between the evaporator and the condenser. Auxiliary devices, such as charge modulators and accumulators are sometimes used with fixed restrictors to suppress the tendency to flood or starve the evaporator. However, these devices are bulky and fairly expensive and have other limitations related to charge variation and heat transfer.

Various devices have been proposed for use in conjunction with fixed flow restrictors as means ing the tendency of such restrictors to either flood or to starve the evaporator under certain operating conditions. Such devices have, in general, either been indirectly controlled in their operation as by means of an electrical control circuit responsive to the condition of the refrigerant leaving the evaporator or have been so closely associated with the fixed flow restrictor as to be only indirectly or slightly responsive to the suction gas condition, which in the operation of any refrigeration system, is a reliable indication of the proper operation thereof. In other words, a highly superheated condition of the refrigerant in the suction line indicates starving of the evaporator while a moist or wet condition thereof indicates a flooding condition in the evaporator.

An object of the present invention is to provide a refrigerantion system including a fixed flow restrictor and low cost means for varying the flow of refrigerant through the fixed flow restrictor in direct response to the condition of the refrigerant leaving the evaporator.

Additional objects-and advantages of the present invention will become apparent from the following description and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In accordance with the present invention, there is provided a refrigeration system including a compressor, a condenser, a conduit including a fixed flow restrictor, an evaporator and a suction line connected in closed series flow refrigerant circuit. A portion of the conduit including one end of the flow restrictor. is disposed adjacent a portion of the suction line and there is provided means for regulating the flow of refrigerant through the flow restrictor in the form of a valve portion disposed adjacent the one end of the flow restrictor and a thermal portion disposed in the suction line and operatively connetced for prevent- "ice to the valve portion. Changes in the condition of the refrigerant leaving the evaporator and flowing through the suction line, or more specifically changes in the temperature thereof, effect a movement of the thermal portion of the regulating means thereby causing movement of the valve portion thereof relative to the one end of the flow restrictor for varying the flow of refrigerant through the flow restrictor. As the thermal portion of the regulating means is disposed within direct heat exchange with the refrigerant in the suction line, it is predominantly responsive to the temperature of the suction gas or refrigerant.

For a better understanding reference may be had to the accompanying drawing in which:

FIGURE 1 is a diagrammatic view of a refrigeration system including one embodiment of the present invention;

FIGURE 2 illustrates a second embodiment of the present invention; and

FIGURE 3 illustrates another embodiment of the invention.

While the invention is applicable to either normal or simple refrigeration systems or to heat pumps, it will be specifically described with reference to a simple or cooling-only refrigeration system.

With reference to FIGURE 1 such a system comprises a compressor 1, condenser 2, a conduit 3 including a fixed flow restrictor 4, an evaporator 5 and a suction line 6 connected in closed series connection whereby the compressor withdraws low pressure refrigerant from the evaporator 5 and discharges high pressure refrigerant to the condenser 2. This high pressure refrigerant condensed in the condenser 2 flows through the flow restrictor 4 into the evaporator.

In the practice of the present invention, the system includes in addition to the flow restrictor 4 a variable flow control or regulating means which variably blocks either the inlet or the outlet to the restrictor 4 in response to changes in the suction gas temperature for the purpose of preventing fiooding or starving of the evaporator over a relatively wide range of operating conditions, refrigerant charges and distances between the evaporator and condenser.

In accordance with the embodiment of the invention illustrated in FIGURE 1 of the drawing, the illustrated portion of the suction line 6 and the illustrated portion of the conduit 3 including the outlet end 8 of the restrictor 4 are positioned adjacent one another and are preferably integrally connected by a rigid connecting portion 9 adapted to support the portion of the suction line 6 and the enumerated portions of the conduit 3 and the restrictor 4 in fixed relationship. A bore or passage 10 extends from the suction line 6 fixed to the portion of the conduit 3 adjacent the outlet of the restrictor 4 and a rod or pin 11 slidably mounted in the bore 10 includes an end portion 12 which functions as a valve for partially restricting the flow of refrigerant from the restrictor 4 under certain conditions of operation of the system. The end of the rod 11 extending into the suction line portion 6 is connected to the free or movable end 14 of a bimetal 15 the other end 16 of which is secured to a wall portion of the suction line.

During operation of the system, the end 14 of the thermal element 15 moves in response to changes in the temperature of the refrigerant flowing from the evaporator through the suction line on its way to the compressor, movement of the bimetal 15 causing the valve forming end portion 12 of the rod 11 to move relative to the outlet end of the restrictor 4 and thereby regulate the flow of refrigerant to the evaporator. The restrictor 4 is designed to provide the desired refrigerant flow under what may be described as the normal or usual operation of the system. In other words, it receives high pressure refrigerant from the condenser 2 and throttles the refrigerant to a low pressure state so that the refrigerant as it leaves restrictor 4 is usually in the form of a mixture of liquid and gas. This refrigerant then flows to the evaporator 5. If the conditions of operation become such that flow permitted by the restrictor 4 becomes excessive, not all of the liquid refrigerant will be evaporated in the evaporator 5 so that some of the refrigerant flowing through the suction line 6 will become wet, that is there will still be some liquid refrigerant carried along with the low pressure gaseous refrigerant. The temperature of the refrigerant in the suction line will then decrease to the saturation temperature corresponding to the refrigerant pressure existing in that line. When the temperature decreases, the thermal element 15 is designed to move the pin 11 to a position in which the end portion 12 partially blocks the restrictor outlet 8 thereby reducing the flow of refrigerant to the evaporator and correcting the tendency to over-feed the evaporator under the existing conditions.

If the flow of refrigerant from the restrictor 4 to the evaporator becomes insufficient, all of the liquid refrigerant will be evaporated in the evaporator with the result that the gas flowing through the suction line 6 will become excessively superheated. The temperature of the refrigerant flowing in contact with the bimetal 15 will then increase so that this thermal element will cause the valve portion 12 of the rod 11 to move away from the restrictor outlet thereby permitting greater flow of refrigerant to the evaporator to correct the superheated condition.

It will be obvious, of course, that for proper operation of the regulating means, the valve portion 12 of the rod 11 should normally partially block the end of the restrictor 4 when the system is functioning normally and the gas flowing through the suction line 6 is in a slightly but not excessively superheated condition. In other words, the system including the flow restrictor 4 and the position of the rod 11 is so designed that when a dry gas with only moderate superheat flows through the suction line 6, the rod 11 partially blocks the outlet end 8 of the restrictor 4.

It will be obvious, of course, that the flow regulating means comprising the rod 11 and the bimetal 15 will operate equally as Well when associated with the inlet end of the restrictor 4 rather than the outlet as illustrated. It will be obvious also that the thermal element or the thermal actuating means can be a bimetal strip such as that illustrated in FIGURE 1 or may be in the form of a metal rod, bar, strip or any other material of any convenient shape that will produce a displacement or movement of a valving portion corresponding to the end 12 of the rod 11 in response to a temperature change in the suction line.

In the embodiment of the invention illustrated in FIG- URE 2 of the drawing in which similar reference numerals are also used to indicate the same or similar parts, the pin 11 is replaced by a metal strip 29 having a fiat end portion 21 extending in front of the end of the restrictor 4 whereby movement of the bimetal actuator 15 in response to suction line temperatures will move the end portion 21 relative to, or more specifically transversely of, the end of the restrictor 4 to increase or decrease the How of refrigerant to the evaporator.

It will be obvious also that the restrictor 4 may be a capillary tube, an orifice, a porous plug or any fixed flow control means. The bore or equivalent means for supporting the pin 11 or the strip 20 should of course fit these members very closely in order to provide a seal with minimum leakage of refrigerant between the conduit 3 and the suction line 6 To minimize the possibility of leakage, the preferred location of the flow regulating means is at the outlet end of the restrictor 4 so that the pressure differences across the bore lli are at a minimum and are substantially less than if the flow regulating means were operatively positioned relative to the inlet end of the restrictor 4. Also by positioning the thermal element 15 upstream from the bore 10 any leakage through the bore 10 will not bias or affect the thermal element.

FIGURE 3 illustrates a refrigerant flow control means similar to those illustrated in FIGURES l and 2 of the drawings except that provision is made for preventing any leakage of refrigerant between the conduit 3 and the suction line 6 in the vicinity of flow regulating means. In this modification, the thermal actuating element is supported in a well 23 which opens into the conduit 3 adjacent the one or the other end of the restrictor 4 and which extends into the suction line 6. This well eliminates leakage from the conduit 3 to the suction line 6 and by forming the walls of the well 23 of a good heat conducting material, the thermal element is directly influenced by the temperature of the refrigerant flowing through the suction line 6.

In this modification of the invention the bimetal member 22 has one end anchored in the bottom of the Well 23 While the free end 24 acts as a valve portion in that it moves relative to the end 25 of the restrictor 4 to increase or decrease the flow through restrictor 4 in response to the changes in the suction gas temperatures as sensed by the portion of the element 22 within the well.

In order to minimize the effect of the temperature of the refrigerant flowing through the conduit 3 on the thermal element, a baflie 27 may be provided at the open end of the well to minimize the entrance of refrigerant from the conduit 3 into the well.

From the above description, it will be seen that there has been provided flow regulating means in combination with a fixed flow restrictor including a thermal actuating element that is completely or predominately responsive to changes in the temperature of the suction gas flowing from the evaporator to the compressor. It will be obvious also that the regulating means need not be positioned at one or the other end of the flow restrictor but could also be used in a system in which there are divided flow restrictors with the regulating means positioned between the two portions.

While there has been shown and described particular embodiments of the present invention, it is to be understood that it is not limited thereto and it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A refrigeration system including a compressor, a condenser, fixed flow restrictor means, an evaporator and a suction line connected in closed series flow refrigerant circuit, said fixed flow restrictor means providing the desired refrigerant flow under normal system operating conditions,

one end of said flow restrictor means being disposed adjacent a portion of said suction line,

and means for regulating the flow of refrigerant through said flow restrictor means to compensate for abnormal system operating conditions comprising a valve portion disposedadjacent said one end and a thermal portion disposed in said suction line for movement of said valve portion relative to said one end in response to changes in the temperature of the refrigerant in said suction line portion for varying the flow of refrigerant through said flow restrictor means. 2. A refrigeration system including a compressor, condenser, capillary tube fixed flow restrictor, an evaporator and a suction line connected in closed series flow refrigerant circuit,

one end of said flow restrictor being disposed adjacent a portion of said suction line,

flow means for varying the fiow of refrigerant through said flow restrictor comprising a valve portion disposed adjacent said one end and a thermal portion disposed in said suction line for movement of said valve portion relative to said one end solely in response to changes in the temperature of the refrigerant in said suction line portion for varying the flow of refrigerant through said flow restrictor.

3. A refrigeration system including a compressor, condenser, a conduit including a capillary tube flow restrictor of substantial length, an evaporator and a suction line connected in closed series flow refrigerant circuit,

a portion of said conduit adjacent one end of said flow rest-rictor being exteriorly connected to said suction line,

a Well opening into said conduit portion and extending into said suction line,

and means for regulating the flow of refrigerant through said flow restrictor comprising a thermal portion disposed in said well and movable in response to changes in the temperature of the refrigerant flowing through said suction line and a valve portion disposed in said conduit adjacent said one end of said restrictor and actuated by said thermal portion to vary the flow of refrigerant through said restrictor in response to changes in the temperature of refrigerant flowing through said suction line.

References Cited by the Examiner UNITED STATES PATENTS 2,463,951 3/1949 Carter 62225 2,520,191 8/1950 Aughey 62-225 2,642,724 6/ 1953 Carter 62-225 FOREIGN PATENTS 23,926 4/ 1931 Netherlands.

MEYER PERLIN, Primary Examiner. 

1. A REFRIGERATION SYSTEM INCLUDING A COMPRESSOR, A CONDENSER, FIXED FLOW RESTRICTOR MEANS, AN EVAPORATOR AND A SUCTION LINE CONNECTED IN CLOSED SERIES FLOW REFRIGERANT CIRCUIT, SAID FIXED FLOW RESTRICTOR MEANS PROVIDING THE DESIRED REFRIGERANT FLOW UNDER NORMAL SYSTEM OPERATING CONDITIONS, ONE END OF SAID FLOW RESTRICTOR MEANS BEING DISPOSED ADJACENT A PORTION OF SAID SUCTION LINE, AND MEANS FOR REGULATING THE FLOW OF REFRIGERANT THROUGH SAID FLOW RESTRICTOR MEANS TO COMPENSATE FOR ABNORMAL SYSTEM OPERATING CONDITIONS COMPRISING A VALVE PORTION DISPOSED ADJACENT SAID ONE END AND A THERMAL PORTION DISPOSED IN SAID SUCTION LINE FOR MOVEMENT OF SAID VALVE PORTION RELATIVE TO SAID ONE END IN RESPONSE TO CHANGES IN THE TEMPERATURE OF THE REFRIGERANT IN SAID SUCTION LINE PORTION FOR VARYING THE FLOW OF REFRIGERANT THROUGH SAID FLOW RESTRICTOR MEANS. 